High-resolution and high-squint spaceborne synthetic aperture radar (SAR) system has excellent earth observation performance. However, high-squint spaceborne SAR data is more challenging to process than the general broadside counterpart because of the severe range-azimuth coupling (RAC). Whereas the classic linear range walk correction (LRWC) method can handle this problem, it is performed in azimuth time-domain and seriously constrains azimuth swath width. In this article, a decoupled hybrid correlation Algorithm (DHCA), combining the range-azimuth decoupling (RAD) in 2-D frequency domain with the modified hybrid correlation (MHC), is proposed to handle sliding spotlight spaceborne SAR data of high-squint angle case. The decoupled hybrid correlation (DHC) is the main body of the proposed algorithm, and it starts with RAD filtering in 2-D frequency domain, which is designed to eliminate the majority of the range cell migration (RCM) and RAC caused by high-squint angles. A nonlinear chirp scaling (NLCS) in range direction is subsequently performed to equalize the variant range chirp rate caused by residual RCM and RAC. Coarse range compression can then be realized uniformly by the range-matched filtering. The NLCS operation and range coarse compression ensure that the range-Doppler (RD) signals of all targets within the whole scene occupy very narrow range cell scopes. By making full use of the principle of stationary point (POSP) to signals, the range compression position and range frequency mapping relationship after NLCS can be derived. The MHC can therefore be fulfilled by extracting the RD signals along the residual RCM and constructing the reference correlation function after the range NLCS. Thus, both the efficiency and the accuracy of focusing processing are guaranteed. Simulations are carried out to validate the proposed algorithm.

中文翻译：

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大斜视星载SAR数据成像解耦混合相关算法


高分辨率大斜视星载合成孔径雷达（SAR）系统具有优异的对地观测性能。然而，由于严重的距离-方位角耦合（RAC），大斜视星载 SAR 数据的处理比一般的舷侧对应数据更具挑战性。虽然经典的线性距离游走校正（LRWC）方法可以解决这个问题，但它是在方位角时域中执行的，并且严重限制了方位角测绘带宽度。本文提出了一种解耦混合相关算法（DHCA），将二维频域距离方位解耦（RAD）与改进的混合相关（MHC）相结合，用于处理大斜视滑动聚束星载SAR数据。角案例。解耦混合相关（DHC）是该算法的主体，它从二维频域的RAD滤波开始，旨在消除大部分由高频引起的距离单元迁移（RCM）和RAC。斜视角度。随后执行距离方向上的非线性线性调频缩放（NLCS）以均衡由残余RCM和RAC引起的变化距离线性调频速率。然后通过范围匹配滤波可以统一实现粗范围压缩。 NLCS操作和距离粗压缩保证了整个场景内所有目标的距离多普勒(RD)信号占据非常窄的距离小区范围。充分利用信号的驻点（POSP）原理，可以推导出NLCS后的距离压缩位置与距离频率映射关系。因此，可以通过沿着残余RCM提取RD信号并在距离NLCS之后构造参考相关函数来实现MHC。 从而保证了聚焦处理的效率和精度。进行仿真以验证所提出的算法。